Vibration reducing device and method



Nov. 10, 1964 D. D. PETTIGRl-:w 3,156,127

VIBRATION REDUCING DEVICE AND METHOD Filed Aug. 2, 1962 2 Sheets-Sheet lQM www AITORNEYJ Nov. 10, 1964 D. D. PETTIGREW VIBRATIDN REDUCING DEVICEAND METHOD 2 Sheets-Sheet 2 Filed Aug. 2, 1962 Inventor Dovd D.Pettigrew M( V United States Patent O 3,156,127 VIBRATION REDUCHNGDEW/ECE AND ME'EHQD David l). Pettigrew, Pittsburgh, Pa., assigner teRockwell Manufacturing Company, Pittsburgh, Pa., a corporation ofPennsylvania Filed Aug. 2, 1962, Ser. No. 214,226 8 Claims. (Cl.I4-230.17)

This invention relates to vibration reducing devices and methods and,more specifically, to devices and methods for eliminating chatteringbetween two rotatively ixed rotary members, one of which is freelyslidable on the other, without impeding the sliding movement. Thepresent invention is especially useful in minimizing the operating noiseof variable speed belt drives by eliminating chattering between thedrive pulley and drive shaft although it is by no means limited to thisapplication.

Conventional variable speed belt drives, such as those shown in UnitedStates Patent No. 2,233,822, issued to W. Schubbe March 4, 1941, forDrilling Machine and in United States Patent No. 2,604,794 issued to F.B. Scott July 29, 1952, for Belt Tensioning Device for Variable-SpeedDrives, include driving and driven pulleys mounted on rotatable shaftsand connected by an endless belt, generally of the V-type. Each of thepulleys has a pulley half which is axially and rotatively iixed to theassociated shaft and a pulley half rotatively fixed to the shaft, butfreely movable or slidable along it. The movable pulley halves areconnected by a speed varying mechanism which simultaneously varies theeffective diameters of the two pulleys in equal amounts, but in theopposite sense, by shifting the respective movable pulley halves towardand away from the associated fixed pulley halves.

Variable speed drives of this type have heretofore Y been plagued bynoisy operation, caused mainly by chattering of the drive pulley on thedrive shaft, especially at low speeds. The present invention eliminatesthis problem, providing quietly operating variable speed belt drives.Broadly speaking, the present invention, as it relates to the particulartype of belt drive described above, resides in fixing a resilient inserthaving a low coefficient of friction between the movable half of thedrive pulley and the drive shaft. It has been found that, surprisingly,this eliminates the chattering without restricting the movement ofthepulley half along the drive shaft.

It is an object of the present invention to provide novel means andmethods for eliminating chattering between two rotatively fixed,rotatable members in a variable speed belt drive, one of which is freelyslidable on the other, without impeding the sliding movement.

Another specific object of lthe present invention resides in theprovision of quietly operating variable speed belt drives.

Another specic object of the present invention is the provision of novelmethods for substantially eliminating the operating noise of variablespeed belt drives.

Yet another specic object of the present invention resides in theprovision of novel means and methods for preventing drive pulleys ofvariable speed belt drives from chattering without impeding the shiftingof the movable drive pulley half aiong the drive shaft.

Additional objects and further novel features of the present inventionwill become fully apparent from the appended claims and as 4the ensuingdetailed description and discussion proceeds in conjunction with theaccompanying drawing, in which:

FIGURE 1 is a side view, partly in section, of a drill head equippedwith a variable speed, V-belt drive incorporating the present invention;

FIGURE 2 is atop plan view of the structure illustrated in FIGURE 1;

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FIGURE 3 is a s1de view, partly in section and to an enlarged scale, ofthe drive shaft and a portion of the drive pulley constructed inaccordance with the present invention; and

FIGURE 4 is a modiiied form of the present invention.

As was pointed out above, the present invention may be advantageouslyemployed to substantially eliminate the operating noise of variablespeed belt drives. In the following detailed description and discussionthe present invention will, therefore, be described in relation to sucha belt drive, the particular drive or transmission illustrated beingthat diselosed and claimed in copending application Serial No. 162,847tiled March 1, 1962, by I. H. Diehl et al. for Power Tool andTransmission Therefor and assigned to the assignee of the presentinvention. It is to be understood, however, that not only is theusefulness of the present invention not limited to the particular beltdrive illustrated, but that it has utility in other such transmissionswhere it is desired to prevent chattering between two rotatively tixedrotary members and, at the same time, permit free sliding movement ofone member upon the other.

Referring now to the drawing, FIGURE 1 illustrates the head 16 of adrill press of the general form illustrated in United States Patent No.2,567,982 issued September 18, 1951 to C. A. Wiken for Machine Tool, andequipped with a variable speed belt drive incorporating the presentinvention. Drill head 1? comprises a head casting or body member 12. Thedrill spindle 142 includes an upper spindle portion 16 journalled incasting 12 by axially spaced anti-friction bearings 18 and 2i? and acoaxial, lower spindle portion 22 mounted on the casting by a quill (notshown) in the conventional manner and connected to the upper spindleportion by splines 24. An electric drive motor 26 with an output shaft28 substantially parallel to the axis of the spindle 14 is secured tocasting 12 by mounting studs Sti in the conventional manner.

Motor output shaft 28 is drive-connected to spindle 14 by a variablespeed V-belt drive comprising a split sheave pulley 32 mounted on themotor output shaft, a split sheave pulley 3ft mounted on upper spindleportion 16, and a V-belt 36 interconnecting pulleys 32 and 34.

Pulley 32 comprises an upper sheave half 33 rotatively and axially fixedto a sleeve 4t! by dowel pin 42, a movable sheave half 44 slidablymounted on sleeve 4d and rotatively fixed thereto by a key 46 which issecured to sleeve 4h and engages an axially extending keyway 48 withinthe bore of movable sheave half hub Sii. Sleeve 4t) is slidably fixed onmotor output shaft 28 by a setscrew S2.

Referring now especially to FIGURE 3, a transversely extendinginternally threaded aperture 54 is formed through movable sheave halfhub 50. Disposed in aperture S4 is a vibration absorbing insert 56 whichis retained in place by a setscrew 58 threaded into aperturevi, at leastthe outer portion of which is internally threaded to retain the setscrewin place. Setscrew 58 is tightened against insert 56 which, preferably,has substantially the same diameter as aperture 54.

The particular material from which vibration absorb ing insert 56 isfabricated is not critical. However, the material selectedshould havethe following properties: l) suticient hardness that there will be nomaterial cold ilow; -(2) a moderate amount of compressive strength; (3)suliicient resiliency to avoid scoring drive sleeve 4d and to absorb anddampen the vibration between sleeve 40 and movable sheave half 44; (4) asuthciently -low coeiiicient of friction that the sliding movement ofmovable sheave half i4 relative to drive sleeve 4d will not be impededor hindered; (5) sufficient wear resistance with the material from whichdrive sleeve 4d is fabricated to insure an adequate useful life; (6)high resistance to oil and the other lubricants which are normally usedin the types of mechanisms in which the present invention is intended tobe incorporated; and (7) adequate thermal resistance to preclude damagefrom the heat generated by operation of the mechanism in which it isemployed. Exemplary materials having the foregoing characteristics whichhave been found suitable for the intended use described above includethe synthetic polymers known cornmercially as nylon and Tefion.

It is not critical that vibration absorbing insert 56 be formed as amember separate from setscrew 53. The desired results may also beachieved by increasing the length of setscrew S8 and providing a heavycoating of nylon, Teflon, or other equivalent material having theproperties described above on its inner end. This modification is shownin FIGURE 4 in which the inner end of the lengthened setscrew,identified by reference character 58a, is surrounded by a coating S9 ofmaterial with the charactristics described above.

Split sheave pulley 34 includes a lower axially fixed sheave half 60.The hub 62 of the fixed sheave half rests upon a fiange 64 integral withupper spindle portion 16 to which it is rotatively fixed by a key 66projecting from its periphery and engaging a longitudinally extendingkeyway 68 formed in the interior wall of the bore of hub 62. The axiallymovable sheave half 70 is rotatively fixed to upper spindle portion 16by a key 72 fixed to spindle portion 16 which engages a longitudinallyextending keyway 74 in the bore of the hub 76 of sheave half 70 Theaxially movable sheave halves 44 and 70 are connected for concomitantaxial displacement by a bracket 78 mounted for rectilinear motion in apath parallel to the axes of output shaft 28 and spindle 14 on acylindrical mounting pin or stud 80 fixed to the top of casting 12 byscrews 82 with its axis parallel to the axes of the motor output shaftand spindle.

Bracket 78 embodies a pair of elongated side members 84 and 86interconnected at their forward end by an inverted U-shaped bracket 8Sand a reinforcing U-shaped bracket 90, adjacent their midpoints by amounting bracket 92, and at their rearward end by an annular collar 94fixed between the side members by mounting screws 96 and 98.

Collar 94 (see FIGURE 1) supports an anti-friction bearing such as ballbearing 100 with its inner race axially confined with respect to sheavehalf hub 50 by retainer rings 102 and 104. Movable sheave half 70 isrotatably suspended from bracket 88 by an anti-friction type bearingsuch as ball bearing 106 with its outer race retained against the upperend of sheave half hub '76 by an internally shouldered and threadedretainer ring 108 and its inner race supported upon a stub shaft 110 byretainer rings 112 and 114. Stub shaft 110 is suspended from bracket 82by its threaded extension 116 which is secured to the bracket by opposedjam nuts 118 and 120.

Central bracket 92 has a vertically extending wall 122 lying parallel tothe axis of pin 80 and top and bottom flanges 124 and 126 which aresuitably apertured and support bearing bushings 128 and 130,respectively. Bearing bushings 128 and 130 are axially slidably receivedupon pin 80. Bracket 92 has forwardly extending side fianges 132 and 134lying parallel to members 84 and S6 and is joined thereby by welding.Bracket 90 and 88 are welded to members 84 and 36 at their opposite endsto provide a rigid assembly.

Upward movement of bracket 7S along pin 80 lifts movable sheave halves44 and 70, increasing the effective diameter of split sheave pulley 32and reducing the effective diameter of split sheave pulley 34, anddownward movement of bracket 78 produces the reverse effect.

The movement of bracket 78 is controlled by a hand wheel or crank 136located at the front end of the drill press and journalled within a bore138 in belt guard casting 140. Crank 136 is fixed by a shear pin 142 toa short shaft 144 journalled in bore 138 to prevent damage to themechanism by attempted speed adjustment while motor 26 is off. Shaft 144is frictionally retained against rotation in bore 138 by a frictionbrake pad 146 pressed against its periphery by a screw 148 to preventinadvertent or spindle load induced rotation of crank 136 or its shaft144. Shaft 144 is connected to bracket 78 by a drive train (see FIGURE2) comprising a pinion 159 fixed to shaft 144, a gear 152 in constantmesh with pinion 150 and mounted for rotation about the axis of a shaft154 which is parallel to shaft 144, a pinion 156 mounted for rotationwith gear 152, and a gear 158 in constant mesh with pinion 156 andmounted upon a shaft 160. Shaft 160 is journalled at one end within thecoaxial end bore 162 (see FIGURE 1) in shaft 144 and, at the other end,in a bore 164 (FIGURE 2) formed in pin 80 and by a bracket 166 fixed tothe top of casting 12 by screws 168. A pinion 170 is fixed to shaft 160between bracket 166, which prevents defiection of shaft 160 upon loadingof pinion 170, and pin 80. Pinion 170 is in constant mesh with avertically extending rack 172 fixed to a bracket 174 by screws 176.Bracket 174 is fixed to the upstanding wall 122 of bracket 94 as bywelding.

Rotation of crank 136 in a clockwise direction produces clockwiserotation of shaft 160 and elevates bracket 78, increasing the speed ofthe spindle; counterclockwise rotation of crank 136 lowers bracket 78,decreasing the spindle speed. In order to provide a direct readingindication of the selected spindle speed, a dial plate 178 is fixed tothe front face of belt guard casting 140. Shafts 150 and 184 are driveconnected by a chain and sprocket drive comprising a sprocket 186 fixedto shaft 160, chain 188, and a sprocket 190 fixed to shaft 184.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiment is therefore to be considered in all respects as illustrativeand not restrictive, the scope of the invention being indicated by theappended claims rather than by the foregoing description, and allchanges which come within the meaning and range of equivalency of theclaims are therefore intended to be embraced therein.

What is claimed and desired to be secured by Letters Patent is:

l. In a variable speed V-belt transmission: a first rotary member; asecond rotary member rotatable with and freely slidable on said firstmember; and means for eliminating chatter between said members withoutirnpeding sliding of the second member on the first comprising a solidvibration absorbing insert of material having a low coefficient offriction carried by one of said members and stop means carried by saidone member biasing said insert into engagement with the other of saidmembers.

2. The variable speed transmission as defined in claim l, wherein saidmaterial is resilient.

3. The variable speed transmission as defined in claim 1, wherein saidmaterial is highly resistant to lubricants.

4. The variable speed transmission as defined in claim 1, wherein saidmaterial is resistant to deterioration in mechanical properties in thepresence of temperatures substantially above room temperature.

5. The variable speed transmission as defined in claim 1, wherein saidmaterial is suiiiciently hard to deterioration in mechanical propertiesto withstand cold flow and has a substantial amount of compressivestrength.

6. In combination: a rotatable shaft; a first pulley half rotatively andaxially fixed on said shaft; a second pulley half rotatively fixed onand freely slidable along said shaft; and means for eliminating chatterwithout irnpeding the sliding of said second pulley half on said shaft,comprising: an aperture in the hub of said second pulley half; avibration absorbing insert having a low coefficient of friction and highresistance to cold 110W in said aperture; and adjustable stop meansoperatively ixed to said hub biasing said insert into engagement Withsaid shaft.

7. The combination as dened in claim 6, wherein said shaft is a drivenshaft.

8. The combination as dened in claim 6, wherein said insert hassubstantially the same diameter as the aperture in said hub.

References Cited in the le of this patent UNITED STATES PATENTS PalmDec. 23, Wright Dec. 11, Shaw Dec. 23, Fineran May 4, Dunn July 30,Davidson Apr. 28, Kiekhafer June 16,

UNITED STATES PATENT oEEIcE CERTIFICATE 0F CORRECTION Patent No., 3,156, 127 November 10Xl 1964 David D. Pettigrew It is hereby certifiedthat error appears in the above numbered patent requiring correction andthat the said Letters Patent should read as corrected below.

Column 1, line 61, after "to" insert deterioration in mechanicalproperties in the presence of lines 67 and 68q strike out "todeterioration in mechanical properties to".,

Signed and sealed this 30th day of March 1965a (SEAL) Attest:

ERNEST W. SWIDER EDWARD .1. BRENNER Attesting Officer Commissioner ofPatents

1. IN A VARIABLE SPEED V-BELT TRANSMISSION: A FIRST ROTARY MEMBER; ASECOND ROTARY MEMBER ROTATABLE WITH AND FREELY SLIDABLE ON SAID FIRSTMEMBER; AND MEANS FOR ELIMINATING CHATTER BETWEEN SAID MEMBERS WITHOUTIMPEDING SLIDING OF THE SECOND MEMBER ON THE FIRST COMPRISING A SOLIDVIBRATION ABSORBING INSERT OF MATERIAL HAVING A LOW COEFFICIENT OFFRICTION CARRIED BY ONE OF SAID MEMBERS AND STOP MEANS CARRIED BY SAIDONE MEMBER BIASING SAID INSERT INTO ENGAGEMENT WITH THE OTHER OF SAIDMEMBERS.